Cylinder machines for grinding a radiused optical lens surface are old in the art. One such cylinder machine is sold by Coburn Optical Industries of Muskogee, Oklahoma. Another such cylinder machine is sold by R. Howard Strasbaugh, Inc. of Long Beach, California. In general, the cylinder machine comprises a lower lens abrading surface or lap adapter that is driven in an oscillatory mode and a pin holder driven in a second oscillatory mode with the pin holder having two drive pins for holding and pushing the lens back and forth over the oscillating lens abrading surface. It is the composite motion of the pin holder and the lap adapter that generates a lens surface wherein the mutually perpendicular cross curves have different radii of curvature. Through use the axis of the pin holders may become misaligned with respect to the axis of the lap adapter. If the axis of the pin holder is not in alignment with the axis of the lap adapter, the cylinder machine grinds a lens with misalignment of the optical axes of the lens. If the radius of curvature of the lens surface is the same in all directions, the optical axis misalignment of the lens does not create any problem; however, if the radius of curvatures are different in mutually perpendicular directions, misalignment of the axis of the pin holder and the axis of the lap adapter produces an unacceptable lens. Since both the lap adapter and the drive pin move relative to one another, it is difficult to determine if the axis of the pin holder is in proper alignment with the axis of the lap adapter unless one manually drives the cylinder machine through a number of full cycles.
The present invention provides an apparatus for checking the alignment of the axis of the drive pin with respect to the axis of the lap adapter regardless of what portion of the abrading cycle the cylinder machine is stopped in and without having to manually drive the cylinder machine through a full cycle.
In general, the prior art method of aligning the axis of the pin holder and the axis of the lap adapter utilize an alignment block and an axis block. The axis block is mounted in the lap adapter and the alignment block having a V-groove extending longitudinally along the top of the alignment block is placed on top of the axis block. The axis misalignment is determined by manually rotating the drive mechanism of the cylinder machine through a number of cycles and observing the rotational displacement on both ends of the block. If the rotational displacement on the ends of the blocks is uneven, one adjusts the axis of pins until it visually appears the rotational displacement of the ends of the blocks are equal as one rotates the drive mechanism through a couple cycles.